Battery-operated sanitary fixture controls which utilize reflected infrared light from an emitter to a receiver to detect the presence of a user and thus initiate water flow, generally are operated by the generation of infrared transmitted pulses or pulse trains at time-spaced intervals, usually periodically, so that the presence of an object or body in the path of the emitted infrared light pulses will reflect the pulses to a receiver and the latter can transduce the received light signal into electrical signals which, in the control and evaluating electronic circuit connected to the sensor, to determine the presence of a user. Water flow can then be initiated based upon the use of the fixture.
Depending upon the evaluation of the electrical signal in the control circuit, a valve can be operated. The valve may be a solenoid or magnetically-operated valve.
To distinguish between foreign infrared radiation and infrared radiation generated by the transmitter or emitter of the sensor, the transmitter is generally pulsed to produce a pulse train or a modulated infrared output. In such systems it is not uncommon to provide individual pulses or shortened pulse trains until detection of an object in the path of the infrared radiation is achieved so that only upon the probable or possible presence of an object, such as the body of a potential user in the detection region will the water flow be commenced. This avoids water flow during inappropriate periods. When detection is plausible, of course, the number of pulses per unit time can be increased or longer pulse sequences or trains can be used to detect the proximity of a user.
These systems, which operate with constant time intervals between the individual transmitted IR pulses or pulse groups, operate independently from the ambient light levels which may be present.
Since the primary current-consuming component of such a water control system for a sanitary fixture is generally the infrared transmitter, because it operates in conventional systems continuously to meet the individual pulses or pulse groups even though the intervals between them may be lengthened until the presence of a user is detected, the useful life of a battery driving the system is greatly limited. Battery change must be carried out frequently and, for sanitary fixtures which must be sealed, the changing operation may be onerous.